This is a map of the distribution of the Woolly Mammoth taken from here. I presume it’s the max range, which was between 30-20K years ago just before the last glacial max started to retreat. Everything above the red and all mountains within the red were glaciated. In North Amercia, most of the area west of the red was glaciated except for a thin ice free strip along the Pacific coast.
I selected this map because it corresponds pretty much exactly to the Mammoth Steppe. I know some folks don’t like Wikipedia and if you’re one of them, feel free to check out any of the 44 citations at the bottom of the following article, which I think is a good description and summation of the Mammoth Steppe.
Significance to our ancestors? In my best Rod Serling voice: “Consider, if you will, looking out upon a pasture like no other, covering contiguously half the land surface of the earth with a sea of grass and supporting herds of animals numbering in the millions”.
For those who want to take the deep dive: